Bleaching process

ABSTRACT

THE BLEACHING ACTION OF SOLUTIONS OF CHLOROCYANURIC ACIDS, SALTS AND COMPLEXES IS IMPROVED AND THE CORROSIVITY OF SUCH SOLUTIONS REDUCED BY THE INCLUSION THEREIN OF A TAURATE OF A SATURATED FATTY ACID.

United States Patent O 3,586,474 BLEACHING PROCESS Xavier Kowalski, St. Louis, Mo., assignor to Monsanto Company, St. Louis, M0. N Drawing. Filed June 11, 1969, Ser. No. 832,489 Int. Cl. D061 3/ 06' U.S. Cl. 8-108 2 Claims ABSTRACT OF THE DISCLOSURE The bleaching action of solutions of chlorocyanuric acids, salts and complexes is improved and the corrosivity of such solutions reduced by the inclusion therein of a taurate of a saturated fatty acid.

BACKGROUND OF THE INVENTION This invention relates to an improved process for bleaching textile materials.

More specifically, this invention is concerned with bleaching processes of the type employing chlorocyanuric acid, salts and complexes as the bleaching agent. Generally, commercial bleaching processes utilizing such agents comprise contacting the fabric to be bleached with a bath containing the agent at temperature, pH, and concentration conditions selected in accordance with the skill of the art depending upon the particular bleaching agent, the textile material, and the degree of bleaching required.

It is common practice in such operations to use various surfactants to insure fast and uniform distribution of the bleach solution throughout the textile materials. Unfortunately, many surfactants, although providing good bleach distribution, decrease the bleaching activity of chlorinated cyanurates.

An additional problem encountered in commercial bleaching operation is that the chlorocyanurates, at the concentrations and temperatures employed, tend to generate significant quantities of explosive and corrosive nitrogen trichloride vapors.

SUMMARY OF THE INVENTION It is an object of this invention to provide improved bleaching processes utilizing agents which provide uniform chlorinated cyanurate distribution, improve the bleaching action of chlorinated cyanurates, and inhibit generation of nitrogen trichloride vapor thereby preventing corrosion problems and eliminating explosion hazards.

These objects are obtained by the use of taurates of saturated fatty acids in the solution. The invention will be better understood from the following description of the preferred embodiments.

DESCRIPTION OF THE PREFERRED EMBODIMENTS chloro,) tetra(monopotassium dichloro,)] penta-isocyanurate or (trichloro,) (monopotassium dichloro,) di-isocyanurate disclosed in U.S. Pat. 3,150,132 or mixtures thereof according to procedures familiar to those skilled in the bleaching art. In accordance with conventional practice, the bleaching solution may contain various sta- 3,586,474 Patented June 22,, 1971 bilizers for the bleaching agent, sequestering agents and the like. The bleaching agent will generally be present in a concentration sufficient to provide -1500 parts/million by weight, or more, of available chlorine. The optimum concentration depends upon the textile to be bleached, contact time employed in a particular process, (usually 10 to 60 minutes), pH (usually 3 to 10.5), temperature (usually 20-100 C.), and degree of bleaching required (less severe bleaching may be required if the textile is to be dyed).

Although generalized information regarding the bleaching step has been set forth to facilitate an understanding of this invention, this step, per se, is well understood in the art and no limitation on the present invention is to be implied from the specific information set forth.

To provide the advantages of this invention, the bath must also contain from 0.01 to 0.5% by weight of a taurate of a saturated fatty acid. Taurates of unsaturated fatty acids containing 10-18 carbon atoms, for example, N-methyl-N-coconut oil acid taurate (predominantly N-methyl-N-lauric acid taurate) are preferred. Such taurates are well-known to those skilled in the chemical art and are commercially available.

After bleaching, the fibers are generally sour d in a sodium bisulfite or other conventional souring bath to remove chlorine, after which they are rinsed and dried.

The invention will be further understood from the following examples.

Example I A swatch of acrylic jersey fabric is bleached for 30 minutes at 210 F. in an aqueous bleach bath having a pH of 3 and containing 0.58 gm./liter trichlorocyanuric acid, 1.0 gm./liter sodium-N-methyl-N-coconut oil acid taurate, and 0.5 gm./ liter sodium hexametaphosphate.

After bleaching, the fabric is soured for 10 minutes at F. in a bath containing 2 gm./liter sodium bisulfite "and then rinsed in water. The whiteness number of the fabric as determined with a Gardner Color Difference Meter is 87. (High whiteness numbers represent superior fabric appearance.)

For purposes of comparison, identical swatches of fabric are bleached according to the above procedure using bleach baths wherein the sodium-N-methyl-N-coconut oil acid taurate is replaced with (a) 1 gm./liter linear alkylbenzene sulfonate (alkyl chain lengths C -C (b) 1 gm./liter ethoxylated nonylphenol (containing 9-10 molecular proportions of ethylene oxide); (c) 1 gm./liter ethoxylated dodecyl phenol (containing 9-10 molecular proportions of ethylene oxide); ((1) 1 gm./liter sodium-N- methyl-N-oleoyl taurate (a taurate of an unsaturated fatty acid); and (e) no surfactant. The whiteness numbers obtained by bleaching in these baths are respectively, 85; 80; 8 1; 93; and 85.

It is seen from the above experiment, that the use of the saturated fatty acid taurate in the bleach bath provides superior results as compared to baths containing no surfactant, (e); baths containing commonly employed surfactants (a), (b), (c); and baths containing unsaturated fatty acid taurate surfactants, (d). The appearance improvement in the fabric is significant in that a whiteness number difference of 1 is visually observable.

Example II The procedure of Example I is repeated with the exception that dichlorocyanuric acid is substituted for trichlorocyanuric acid in the bleach bath. Similar results are obtained.

Example III Bleach baths containing about 0.88 gm. trichlorocyanuric acid and the quantities of various surfactants shown in Table 1 below are prepared and heated to about 212 F.

Small coupons of stainless steel 316 are maintained in each bath and in the vapor above, each bath for 5 hours. The corrosion rate of each coupon (expressed in mils/ year) is reported in Table 1.

TABLE 1 Coupon corrosion (mils/yr.)

Bath No. Surfactant In vapor In bath 1 None 35 10 2 .5 gmJliter sodlum-N-methly-N- 6.29 3. 49

coconut oil acid taurate. 3 1 gm./liter sodium-N-methyl-N- 0. 1. 90

coconut oil acid taurate. 4 1.5 gin/liter sodium-N-methyl-N- 23 3. 80

coconut oil acid taurate. 5 .5 gm./1iter tetrapropylene derived 34. 86 8.

benzene sulfonate.

It is seen from the above data that corrosivity of chlorocyanuric acid solutions (due to evolution of NCl is eifectively reduced by the addition to the bath of saturated fatty acid taurates. It is further seen that the use of conventional surfactants such as alkylbenzene sulfonates is significantly less effective.

What is claimed is:

1. In a process for bleaching chlorine bleachable textile fibers by contacting said fibers with an aqueous bleaching bath consisting essentially of a bleaching agent selected from the group consisting of dichlorocyanuric acid; trichlorocyanuric acid; alkali metal salts of said acids; (mono-trichloro,) tetra-(monopotassium dichloro,) penta-isocyanurate or (trichloro,) (monopotassium dichloro,) di-isocyanurate; and mixtures thereof, the improvement wherein said bath contains from 0.01 to 0.5% by weight of a taurate of a saturated fatty acid containing from 10 to 18 carbon atoms.

2. The process of claim 1 wherein said taurate is sodium- N-methyl-N-coconut oil acid taurate.

References Cited UNITED STATES PATENTS 3,281,364 10/1966 Shere et a1. 25299 3,297,578 1/1967 Crutchfield et a1. 25299 MAYER WEINBLATT, Primary Examiner U.S. Cl. X.R. 25295, 99, 187

222,3? UNILED s'm'mzs PA'IIZNT OFFICE CERTIFICATE OF CORRE TEON 3 ,586 ,um Dntd June 22 1971 Patent No.

w i Inventor 8 Yaw T K0 a1 k It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected :18 shown below:

Column 2,

line 5%; the series of numbers reading 8U 81 9 3 g and 85 f should read 8U 81 83; and 85.

Signed and sealed 'this' 2nd day r May 1972.

(SEAL) Attest:

EDWARD M.PLETCHER,JR. Attesting Officer ROBERT GOTTSGHALK Commissioner of Patents 

